Chemical sensor platform has been designed for analysis of the soil macronutrients, namely nitrate (NO3−), monobasic phosphate (H2PO4−), potassium (K+), calcium (Ca2+) and, magnesium (Mg2+) and for measuring the uptake of these nutrients in plants. The use of the chemical sensor platform can be extended to measurement of ionic contamination in rivers and ground water to detect any excessive use of fertilizers, and ionic poisoning of agriculture products. Environmental pollution as a result of excessive use of nitrate and phosphate has been well documented all over the world. Research results have shown that nitrate poisoning of vegetables such as carrot is detrimental to human early growth.
Existing ion selective electrodes specific for anion typically have poor response characteristics including small linear ranges, high detection limits, and many interferences. Prior attempts to design such anion-specific electrode have been met with considerable difficulty. There is a need for a phosphate ion selective electrode having good selectivity and response characteristics employing existing electrode designs. With the availability of a usable ion selective electrode, non destructive techniques for the measurement of phosphate anions by an ion selective electrode can be applied to all areas of measurement science including environmental, medical and industrial applications.
Polymeric hydrophobic membranes embedded with specific molecules capable of ion recognition (ionophore) give ion selective electrode (ISE) or ion sensitive field effect transistor (ISFET) chemical sensor have the ability to selectively measure the activity and concentration of chemical species.
U.S. Pat. No. 5,380,423 discloses a membrane that is selective for anions, particularly phosphate, comprising an ionophore based on a uranyl complex.
U.S. Pat. No. 6,540,894 B2 discloses a phosphate ion selective electrode, which enables selective measurement of phosphate ion concentration, which is regarded as an important indicator of eutrophication in lakes, marshes, etc. and a method of manufacturing this phosphate ion selective electrode.
U.S. Pat. No. 5,380,423 discloses an anion-selective membrane, in particular a membrane that is selective for the phosphate ion, particularly dihydrogen phosphate. This patent further discloses a sensor in which such an anion-selective membrane is included wherein such sensors are used for measuring the concentration of the anion in an electrolyte solution such as fertilizer dosages in the market gardening sector.
The present invention discloses novel anion ionophores that are lipophilic or which can be covalently bonded to polymeric sensing membrane. More specifically the invention relates to the synthesis of ionophore for monobasic phosphate anion (H2PO4−) having high lipophilicity or can be immobilized through cross-linking of the long-chain (C12 to C21) acrylate moiety with polymer backbone or covalently bonded to backbone of polymeric sensing membrane. The ion recognition molecule is a component in hydrophobic membrane intended for analysis of monobasic phosphate anion (H2PO4−) plant nutrient in soil, artificial media, plant sap and hydro phonic liquid, and phosphate pollutant in rivers and ground water.